1. Field of the Invention
The present invention relates to a camera with a magnetic recording/reading device. More particularly, the present invention relates to a camera in which data is read from, and written into, a magnetic recording layer formed on photo film.
2. Description of the Related Art
Known cameras, disclosed in International Publications WO 90/04201 and 90/04202, read data from, and write data into, a transparent magnetic recording layer formed on photo film, during movement of the film. A magnetic head is used, which is disposed in a film passageway of the camera. Examples of magnetic data stored during film manufacture are the kind and sensitivity of the film, and the number of the available exposures on the film. Examples of magnetic data written in the recording layer during photography are a shutter speed, a date, magnification, and information specifying conditions in printing a photograph as instruction to photofinisher. The magnetic head is mounted on a film support plate together with a magnetic recording/reading circuit. This structure is compact and facilitates assembly.
In a conventional camera, a camera body has a hinged back door. In the camera body is formed an exposure aperture, of which the rear is an exposure frame. The exposure frame has a pair of inner rails for positioning the film in a direction of the optical axis of the camera, and a pair of outer rails for guiding longitudinal edges of the film. A film support plate or pressure plate is mounted on the back door via a spring coil or a spring plate. The outer rails closely contact the film support plate, which defines a film passageway between it and the exposure frame like a tunnel. Because it is mounted on the spring member, the film support plate is shiftable in the direction of the optical axis of the taking lens and vertically with respect to the film. The film support plate is shiftable also in the direction of the vertical optical axis, only to a smaller extent. Also, it is known to use a film support plate mounted directly on a camera body by a spring.
To allow smooth movement of the film, the interval between the outer rails is slightly greater than a width of the film. The film thus tends to be off-center between the outer rails during movement, and leans on either one of the outer rails. Even when the magnetic head is positioned accurately, the relative position of the film to the magnetic head tends to change. Even if precision is raised in mounting the magnetic head on the film support plate, the relative position of the film to the magnetic head also tends to change, due to the shift of the film support plate from the camera body. Therefore the magnetic head fails to trace a track of the recording layer accurately. Accordingly, errors in reading and writing data are common. Occasionally the film moves in a zigzag fashion within the film passageway, and the film support plate moves irregularly in a direction of the width of the film. Those cause azimuth deviation of the magnetic head. The photo film has a thickness much greater than audio or video magnetic tape, and has greater rigidity and curling tendency, so that track deviation and azimuth deviation are created to all the greater extent.
Simple resolution of such track deviation could be made by the use of a magnetic head having an enlarged width as compared with a width of the recording layer. However, even such a widened magnetic head cannot cope with azimuth deviation, created by the film moved in zigzag fashion within the film passageway, or by the film support plate moved irregularly in a direction of the width of the film.
Known devices for preventing track deviation and azimuth deviation are disclosed in International Publications WO 90/06536 and WO 91/05288 and JP-A (Japanese Patent Laid-Open Publication No. 3-202830). In those documents, mechanisms for supporting the magnetic head and the film support plate are so improved that the magnetic head and the film support plate are caused to follow a zigzag movement of the film.
However, such a construction, causing the magnetic head or the film support plate to follow a zigzag movement of the film, requires a device for detecting the zigzag movement, a mechanism for moving the magnetic head and the film support plate, and a linking mechanism. It is inevitable that a camera with this construction is highly expensive, because the number of parts and the number of assembling processes are large. It would be conceivable to raise precision of the outer rails and to form a film passageway with a width determined accurately, while positioning pins would be formed on a film support plate, in order that the pins would position the film support plate relative to the camera body. However, the expense of manufacturing a camera with this construction is also high. This is because precision in relative position between the recording layer and a magnetic head fixed on the film support plate could not be raised, unless precision is ensured in relative position between the magnetic head and the film support plate, in position of the pins relative to the film support plate, and in position of the pins relative to the camera body.